News of Andrea’s death was first reported on Friday (6 January) by TMZ Sport.
Jenner, 67, mourned Andrea’s death in a heartfelt Instagram post late on Friday evening, writing that she is “so heartbroken by the sudden passing of Tristan’s mom”.
Alongside a photograph of her, Andrea, Tristan, and Kardashian, Jenner’s caption read: “You were the most amazing, dedicated, devoted, and selfless mom and such a loving, kind, and fabulous grandmother.”
Tristan, 31, and Kardashian share two children – five-year-old daughter True, and a newborn son whose name has not yet been revealed.
Jenner’s post continued: “What a blessing you were to your family!!! I will miss you Andrea. I will miss your bright spirit and amazing light.
“Thank you for always praying for us and lifting us up and encouraging us along the way. Rest in peace beautiful angel.”
Kardashian and Tristan’s on-again, off-again relationship came to a head in December 2021 after it was revealed the NBA star had fathered a child with personal trainer Maralee Nichols while he was still dating the Good American jeans founder.
Tristan apologised to Kardashian after a paternity test revealed he was the father of Nichols’s son, born on 2 December.
In July last year, it was confirmed that the pair were expecting their second child via surrogacy after the baby was conceived in November.
Last month, Tristan and Nichols reportedly agreed to a child support deal more than a year after she filed a paternity lawsuit against him.
Tristan also shares a son, Prince, 4, with ex-girlfriend Jordan Craig.